Page 99 finds me in the midst of retrospection, asking how it could make sense to affirm my actual life as a professor when I believe I should been a physician instead. Looking back at my foolish decision, am I condemned to wish for a second chance?

It is not just about me. There is a wider question here, about regret in the face of our mistakes and the misfortunes that befall us. Is there space between the things you should not have done, or should not have had to endure, and what you should want to change about your past?

Turns out there is. What matters is not the bare existence of what you did, or what has happened to you, as if its mere occurrence made it better, but immersion in the subsequent details of your life, the intricate fabric of moments, relationships, and activities that make it good, even though it is not the best. My relationship to life as a philosopher, in living it, is utterly different from my speculative relationship to an imagined life as a physician.

There is a difference between knowing that something is worthwhile and knowing what makes it so, between knowing the existence of reasons for desire and knowing what those reasons are. Just as it is rational to respond less strongly to the abstract knowledge that your life will have deficiencies than to learning which ones, so it is rational to respond more strongly to the definite ways in which a life is good than to the nebulous fact that another life is better.

Hence the advice with which the chapter ends: “Do not weigh alternatives theoretically, but zoom in: let the specifics count against the grand cartoon of lives unlived. In doing so, you may find that you cannot regret that you should have resisted at the time.”

This is from a chapter about dealing with the past. Other chapters confront the relentless grind of necessity, the distortions of nostalgia and the problem of missing out, mortality and fear of death, the tyranny of projects and the challenge of living in the present. A cerebral self-help book, Midlife uses philosophical arguments and ideas as cognitive therapy, speaking to the many midlife crises, and to anyone coping with the irreversibility of time.